Forced flow steam generator



Sept. 14, 1965 o. SCHWARZ 3,205,868

FORCED FLOW STEAM GENERATOR Filed Aug. 10, 1962 2 Sheets-Sheet l FIG.1

12A 125 2C 12D 38 16 INVENTOR.

Orrmar Schwarz ATTORNEY Sept. 14, 1965 o. SCHWARZ 3,205,868

FORCED FLOW STEAM GENERATOR Filed Aug. 10, 1962 2 Sheets-Sheet 2 FIG. 3

INVENTOR. Orrmar Schwarz ATTORNEY United States Patent 3,205,868 FORCED FLOW STEAM GENERATOR Ottmar Schwarz, Ratingen, Germany, assiguor to Durrwerlre Aktiengesellschaft, Ratiugen, Germany, a corporation of Germany Filed Aug. 10, 1962, Ser. No. 216,088 4 Claims. (Cl. 122-1) This invention relates in general to forced flow fluid heating units and more particularly to improvements in the construction and operation of fluid heating circuits adapted for use in a recirculating forced flow vapor generating and superheating unit.

In a unit of the character described it is usual practice to provide parallel flow vapor generating circuits having their discharge ends connected to a common steam and water separating drum. This construction is disadvantageous in that it requires the use of a thick-walled drum, particularly for units of high pressures and high capacities, and the use of relatively complex vapor generating tube arrangements. These requirements add much to the cost of the unit. Further, during operation of such units the water level in the drum is diflicult to control and the time required to start up the unit is relatively prolonged because of the thermal stresses induced in the thick drum walls by temperature changes.

The present invention eliminates the aforementioned disadvantages and difliculties of prior units by the provision of a special construction and arrangement of the vapor generating section of the vapor generator. In accordance with the invention a forced circulation vapor generator is provided with an economizer section supplied with vaporizable liquid, a vapor generating section including a plurality of parallel flow vapor generating circuits, and a vapor superheating section. Each vapor generating circuit comprises a steam and water separating vessel arranged to operate with a vapor space above a body of liquid therein and connected for direct supply of liquid from the economizer, with a vapor generating tube group connected for discharge of a mixture of vapor and liquid into the vapor space of the separator. Each vapor generating circuit is also provided with a recirculation pump connected to withdraw liquid from its corresponding separator and to introduce it into its corresponding vapor generating tube group, with the separator of each vapor generating circuit being connected for flow of vapor to the vapor superheating section. Provisions are also made to maintain the liquid level in each of the separators substantially constant. This construction and arrangement eliminates the use of the thick-walled drum required by prior units, permits the use of uncomplicated vapor generating tube arrangements, provides close control of the water level in the respective separators and avoids significantly large water level fluctuations, and enables faster start-ups compared to the time required to place into service drum type forced circulation vapor generators.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a schematic representation of fluid heating circuits constructed and operable in accordance with the invention and particularly adapted for use in a forced circulation recirculation type vapor generator;

FIG. 2 is a schematic representation of a modified form of the circuitry of FIG. 1; and

ice

FIG. 3 is a schematic representation of another modified form of the circuitry of FIG. 1.

Similar reference characters refer to similar parts throughout the drawings.

As forced circulation vapor generators of the recirculating type are well known, I have shown the elements of such a generator in rudimentary form to assist in understanding my invention. The main portions of the unit illustrated in FIG. 1 include a vapor generating section 10 connected for series flow of fluid from an economizer section 12 and to a vapor superheating section 14. Feedwater at high pressure is supplied by a feed pump 16 to the economizer 12 wherein it is partially heated before passing to the vapor generating section 10.

Vapor generating section 10 includes a multiplicity of vapor generating circuits 10A, 10B, 10C, 10D arranged for parallel flow of fluid therethrough relative to each other and having their supply and discharge ends respectively connected to common inlet and outlet headers or conduits 20 and 22, with the header 20 being arranged to receive liquid from the economizer 12 and header 22 being arranged for discharge of vapor to the vapor superheating section 14.

Each of the parallel flow vapor generating circuits 10A, 10B, 10C, 10D comprises a steam and water separator 24 having a normal water level separating an upper steam space from a lower water space and supplied with feedwater by a conduit 26 having its inlet end connected to the header 20 and its outlet end connected to the separator 24 at a position below the water level therein, with the water level in the separator being maintained constant by means of a valve 28 in the conduit 26 suitably regulated by a control unit 30. Water from the water space of each separator 24 flows downward through a downcomer 29 to a recirculation pump 32, then passes through a vapor generating tube group 34 normally subject to high temperature heating gases and connected for discharge of steam and water mixtures into the steam space of the separator 24. In the separator 24 the excess water circulated separates out and, together with feedwater supplied to the separator, is returned through downcomer 29 to the circulating pump 32 for another round trip. Separated steam discharges from the steam space of each of the separators to the common steam collecting header 22, then passes through the vapor superheating section 14 to a header 36, from which it passes to the point of use.

In the embodiment shown in FIG. 2 economizer section 12 comprises four tube groups 12A, 12B, 12C, 12D connected for parallel flow of fluid from a common supply header 38 to which feedwater is delivered by pump '16, with each tube group being connected to a corresponding conduit 26 for supply of preheated feedwater to a corresponding separator 24. Otherwise, the vapor generating circuitry is the same as that of FIG. 1. Superheating section 14 also comprises four parallel tube groups 14A, 14B, 14C, 14D arranged to discharge to a comm-on collecting header 40 from which the collected superheated steam passes to header 36, with each tube group being connected for supply of saturated steam from a corresponding separator 24.

In the form of the invention shown in FIG. 3, the economizer and vapor generating sections are of the same physical character and are interconnected to the vapor generating circuitry in the same manner as the construction of FIG. 1. In operation feed pump 16 forces water through the economizer 12 to header 20 for parallel flow through the valve-controlled conduits 26 to the separators 24. Three circulating pumps 32A, 32B, 32C, aspirate the water in the separators downward by way of downcomers 29 and a header 46, which is connected to the downcomers and to the suction side of each pump, and pump the water to a common head-er 48 for parallel supply of fluid to the vapor generating tube groups 34, each of which is connected for discharge of steam-water mixtures to a corresponding separator 24. In the separators the excess Water circulated separates out and, along with feed Water supplied to .the separators, is returned through the downcomers 29 to the pumps 32A, 32B, 32C for another passage through the vapor generating tube groups 34. Separated steam flows from the separators through the superheating section 14 to the hot steam line 36. This construction has the advantage that the number of recirculating pumps may be reduced or that a recirculation pump may be maintained in reserve.

While in accordance with the provisions of the statutes I have illustrate-d and described herein the best form and mode of operation of the invention now known to me, those skilled in the art Will understand that changes may be made in the form of the apparatus disclosed Without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage Without a corresponding use of other features.

What is cl aim-ed is:

1. In a vapor generator having a forced circulation fluid circulation system;

(a) an economizer section;

(b) means supplying vaporizable liquid to said economizer section, said last named means including a pump providing the entire supply of vaporizable liquid to said economizer section so that the pressure throughout the inlet side of the econornizer section is substantially uniform;

(c) a vapor superheating section; V

(d) a vapor generating section including a plurality of parallel flow vapor generating circuits each comprising (l) a steam and water separating vessel arranged to operate with a vapor space above a body of liquid therein and connected for direct supply of liquid from said economizer;

(2) a vapor generating tube group connected for discharge of a mixture of vapor and liquid into the vapor space of said separator,

(3) .a recirculation pump connected to Withdraw liquid from said separator and to introduce it into said tube group;

(e) means connecting each of said separators for flow of vapor to said vapor superheating section; and

(-f) means for maintaining the liquid level in each of said separators substantially constant.

2. -In a vapor generator having a forced circulation fluid circulation system;

(a) an economizer section including a plurality of parallel flow liquid heating circuits;

(b) means supplying vaporizable liquid to said economizer section, said last named means including a pump providing the entire supply of vaporizable liquid to said economizer section so that the pressure throughout the inlet side of the economizer section is substantially uniform;

(c) a vapor superheating section;

(d) a vapor generating section including a plurality of parallel flow vapor generating circuits each comprising (1) a steam and water separating vessel arranged to operate with a vapor space above a body of liquid therein and connected for direct supply of liquid from one of the liquid heating circuits of said economizer,

(2) a vapor generating tube group connected for I discharge of a mixture of vapor and liquid into the vapor space of said separator,

(3) 1a recirculation pump connected to Withdraw liquid from said separator and to introduce it into said tube group;

(e) means connecting each of said separators for flow of vapor to said vapor superheating section, and

(t) means for maintaining the liquid level in .each of said separators substantially constant.

3. In a vapor generator having a forced circulation fluid circulation system;

(a) an economizer section;

(b) means supplying vaporizable liquid to said economizer section, said last named'means including a pump providing the entire supply of vaporiz'able liquid to said economizer section so that the pressure throughout the inlet side of the economizer section is substantially uniform;

(c) a vapor superheating section including a plurality of parallel flow vapor heating circuits;

(d) a vapor generating section including a plurality of parallel flow vapor generating circuits each comprising (1) a steam and Water separating vessel arranged to operate with a vapor space above a body of liquid therein and connected for direct supply of liquid from said economizer,

(2) a vapor generating tube group connected for discharge of a mixture of vapor and liquid into the vapor space of said separator,

(3) a recirculation pump connected to Withdraw liquid from said separator and to introduce it into said tube group;

(e) means connecting each of said separators for flow of vapor to a corresponding vapor heating circuit of said vapor superheating section; and

( t) means for maintaining the liquid level in each of said separators substantially constant.

4. In a vapor generator having a forced circulation fluid circulation system;

(a) an economizer section including .a plurality of parallel flow liquid heating circuits;

(b) means supplying vaporizable liquid to said economizer section, said last named means including a pump providing the entire supply of vaporizable liquid to said economizer section so that the pressure throughout the inlet side of the economizer section is substantially uniform;

(c) a vapor superheating section including a plurality of parallel flow vapor heating circuits;

(d) a vapor generating section including a plurality of parallel flow vapor generating circuits each comprismg (1) a steam and water separating vessel arranged to operate with a vapor space above a body of liquid therein and connected for direct supply of liquid from one of the liquid heating circuits of said e-conomizer,

(2) a vapor generating tube group connected for discharge of a mixture of vapor and liquid into the vapor space of said separator,

(3) a recirculation pump connected to Withdraw liquid from said separator and to introduce it into said tube group;

(e) means connecting each of said separators for flow of vapor to a corresponding vapor heating circuit of said vapor superheating section; and

. (f) means formaintaining the liquid level in each of said separators substantially constant.

References Cited by the Examiner UNITED STATES PATENTS 2,702,026 2/55 Dalin 122-448 FOREIGN PATENTS 1,108,442 1/5 6 France.

159,707 10/40 Germany. 971,815 4/59 Germany. 501,275 2/ 3 9 Great Britain.

' PERCY L. PATRICK, Primary Examiner. 

1. IN A VAPOR GENERATOR HAGING A FORCED CIRCULATION FLUID CIRCULATION SYSTEM LINES 3 TO 7 ILLEGIBLE. PRESSURE THROUGHOUT THE INLET SIDE OF THE ECONOMIZER SECTION IS SUBSTANTIALLY UNIFORM; (C) A VAPOR SUPERHEATING SECTION; (D) A VAPOR GENERATING SECTION INCUDING A PLURALITY OF PARALLEL FLOW VAPOR GENERATING CIRCUITS EACH COMPRISING (1) A STEAM AND WATER SEPARATING VESSEL ARRANGED TO OPERATE WITH A VAPOR SPACE ABOVE A BODY OF LIQUID THEREIN AND CONNECTED FOR DIRECT SUPPLY OF LIQUID FROM SAID ECONOMIZER; 